Holzinger Andreas, Albert Andreas, Aigner Siegfried, Uhl Jenny, Schmitt-Kopplin Philippe, Trumhová Kateřina, Pichrtová Martina
Department of Botany, Functional Plant Biology, University of Innsbruck, Sternwartestraße 15, 6020, Innsbruck, Austria.
Research Unit Environmental Simulation, Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt GmbH, Ingolstaedter Landstr. 1, 85764, Neuherberg, Germany.
Protoplasma. 2018 Jul;255(4):1239-1252. doi: 10.1007/s00709-018-1225-1. Epub 2018 Feb 22.
Species of Zygnema form macroscopically visible mats in polar and temperate terrestrial habitats, where they are exposed to environmental stresses. Three previously characterized isolates (Arctic Zygnema sp. B, Antarctic Zygnema sp. C, and temperate Zygnema sp. S) were tested for their tolerance to experimental UV radiation. Samples of young vegetative cells (1 month old) and pre-akinetes (6 months old) were exposed to photosynthetically active radiation (PAR, 400-700 nm, 400 μmol photons m s) in combination with experimental UV-A (315-400 nm, 5.7 W m, no UV-B), designated as PA, or UV-A (10.1 W m) + UV-B (280-315 nm, 1.0 W m), designated as PAB. The experimental period lasted for 74 h; the radiation period was 16 h PAR/UV-A per day, or with additional UV-B for 14 h per day. The effective quantum yield, generally lower in pre-akinetes, was mostly reduced during the UV treatment, and recovery was significantly higher in young vegetative cells vs. pre-akinetes during the experiment. Analysis of the deepoxidation state of the xanthophyll-cycle pigments revealed a statistically significant (p < 0.05) increase in Zygnema spp. C and S. The content of UV-absorbing phenolic compounds was significantly higher (p < 0.05) in young vegetative cells compared to pre-akinetes. In young vegetative Zygnema sp. S, these phenolic compounds significantly increased (p < 0.05) upon PA and PAB. Transmission electron microscopy showed an intact ultrastructure with massive starch accumulations at the pyrenoids under PA and PAB. A possible increase in electron-dense bodies in PAB-treated cells and the occurrence of cubic membranes in the chloroplasts are likely protection strategies. Metabolite profiling by non-targeted RP-UHPLC-qToF-MS allowed a clear separation of the strains, but could not detect changes due to the PA and PAB treatments. Six hundred seventeen distinct molecular masses were detected, of which around 200 could be annotated from databases. These results indicate that young vegetative cells can adapt better to the experimental UV-B stress than pre-akinetes.
双星藻属的物种在极地和温带陆地生境中形成肉眼可见的垫子，在那里它们会受到环境压力。对三个先前已鉴定的分离株（北极双星藻属B、南极双星藻属C和温带双星藻属S）进行了实验紫外线辐射耐受性测试。将幼嫩营养细胞（1个月大）和前运动细胞（6个月大）的样本暴露于光合有效辐射（PAR，400 - 700纳米，400微摩尔光子·平方米·秒），同时结合实验性紫外线A（315 - 400纳米，5.7瓦·平方米，无紫外线B），标记为PA，或紫外线A（10.1瓦·平方米） + 紫外线B（280 - 315纳米，1.0瓦·平方米），标记为PAB。实验期持续74小时；辐射期为每天16小时PAR/紫外线A，或每天额外14小时紫外线B。有效量子产率通常在前运动细胞中较低，在紫外线处理期间大多降低，并且在实验期间幼嫩营养细胞的恢复明显高于前运动细胞。叶黄素循环色素的脱环氧化状态分析显示，双星藻属C和S有统计学上显著的（p < 0.05）增加。与前运动细胞相比，幼嫩营养细胞中紫外线吸收酚类化合物的含量显著更高（p < 0.05）。在幼嫩营养的双星藻属S中，这些酚类化合物在PA和PAB处理后显著增加（p < 0.05）。透射电子显微镜显示在PA和PAB条件下，超微结构完整，蛋白核处有大量淀粉积累。PAB处理的细胞中电子致密体可能增加以及叶绿体中出现立方膜可能是保护策略。通过非靶向RP-UHPLC-qToF-MS进行的代谢物谱分析能够清晰区分菌株，但未检测到PA和PAB处理引起的变化。检测到617个不同的分子质量，其中约200个可从数据库中注释。这些结果表明，幼嫩营养细胞比前运动细胞能更好地适应实验性紫外线B胁迫。
